/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License.  You may obtain a copy
 * of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent.testing;

import static com.google.common.util.concurrent.MoreExecutors.directExecutor;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.util.concurrent.ListenableFuture;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

import junit.framework.Assert;

/**
 * A simple mock implementation of {@code Runnable} that can be used for testing ListenableFutures.
 *
 * @author Nishant Thakkar
 * @since 10.0
 */
@Beta
@GwtIncompatible
public class MockFutureListener implements Runnable
{
    private final CountDownLatch countDownLatch;
    private final ListenableFuture<?> future;

    public MockFutureListener(ListenableFuture<?> future)
    {
        this.countDownLatch = new CountDownLatch(1);
        this.future = future;

        future.addListener(this, directExecutor());
    }

    @Override
    public void run()
    {
        countDownLatch.countDown();
    }

    /**
     * Verify that the listener completes in a reasonable amount of time, and Asserts that the future
     * returns the expected data.
     *
     * @throws Throwable if the listener isn't called or if it resulted in a throwable or if the
     *                   result doesn't match the expected value.
     */
    public void assertSuccess(Object expectedData) throws Throwable
    {
        // Verify that the listener executed in a reasonable amount of time.
        Assert.assertTrue(countDownLatch.await(1L, TimeUnit.SECONDS));

        try
        {
            Assert.assertEquals(expectedData, future.get());
        }
        catch (ExecutionException e)
        {
            throw e.getCause();
        }
    }

    /**
     * Verify that the listener completes in a reasonable amount of time, and Asserts that the future
     * throws an {@code ExecutableException} and that the cause of the {@code ExecutableException} is
     * {@code expectedCause}.
     */
    public void assertException(Throwable expectedCause) throws Exception
    {
        // Verify that the listener executed in a reasonable amount of time.
        Assert.assertTrue(countDownLatch.await(1L, TimeUnit.SECONDS));

        try
        {
            future.get();
            Assert.fail("This call was supposed to throw an ExecutionException");
        }
        catch (ExecutionException expected)
        {
            Assert.assertSame(expectedCause, expected.getCause());
        }
    }

    public void assertTimeout() throws Exception
    {
        // Verify that the listener does not get called in a reasonable amount of
        // time.
        Assert.assertFalse(countDownLatch.await(1L, TimeUnit.SECONDS));
    }
}
